Wireless power transmitter and power transmission method thereof

ABSTRACT

Disclosed are a wireless power transmitter and a power transmission method thereof. The wireless power transmitter includes a plurality of transmission resonance units, a detection power applying unit applying detection power to the transmission resonance units to detect a location of the wireless power receiver, and a current measuring unit measuring current generating from a transmission coil unit of the wireless power transmitter based on the applied detection power. The wireless power transmitter transmits the power through at least one transmitting resonance unit corresponding to the location of the wireless power receiver based on the measured current.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 119 of KoreanPatent Application No. 10-2011-0113288, filed Nov. 2, 2011, which ishereby incorporated by reference in its entirety.

BACKGROUND

The disclosure relates to a wireless power transmission technology. Inmore particular, the disclosure relates to a wireless power transmittercapable of effectively transmitting energy by using a resonancephenomenon and a power transmission method thereof.

A wireless power transmission or a wireless energy transfer refers to atechnology of wirelessly transferring electric energy to desireddevices. In the 1800's, an electric motor or a transformer employing theprinciple of electromagnetic induction has been extensively used andthen a method for transmitting electrical energy by irradiatingelectromagnetic waves, such as radio waves or lasers, has beensuggested. Actually, electrical toothbrushes or electrical razors, whichare frequently used in daily life, are charged based on the principle ofelectromagnetic induction. Until now, the long-distance transmissionusing the magnetic induction, the resonance and the short-wavelengthradio frequency has been used as the wireless energy transfer scheme.

In the case of a short-distance wireless power transmission, which hasbeen spotlighted in these days, a wireless power transmitter isinstalled in a building in such a manner that a mobile device, such as acellular phone or a notebook computer, can be continuously charged whena user uses the mobile device in the building even if the mobile deviceis not connected to an additional power cable.

However, according to the wireless power transmission technology of therelated art, power must be constantly transmitted regardless of theexistence of the wireless power receiver that receives the power,causing the waste of the power and damage to the human body.

BRIEF SUMMARY

The disclosure provides a wireless power transmitter capable oftransmitting energy by using a resonance phenomenon and a methodthereof.

In addition, the disclosure provides a wireless power transmittercapable of detecting the location of a wireless power receiver and amethod thereof.

Further, the disclosure provides a wireless power transmitter capable oftransmitting energy through a specific transmission resonance unitcorresponding to the location of the wireless power receiver and amethod thereof.

According to the embodiment, there is provided a wireless powertransmitter for wirelessly transmitting power to a wireless powerreceiver by using resonance. The wireless power transmitter includes aplurality of transmission resonance units, a detection power applyingunit applying detection power to the transmission resonance units todetect a location of the wireless power receiver, and a currentmeasuring unit measuring current generating from transmission coil unitof the wireless power transmitter based on the applied detection power.The wireless power transmitter transmits the power through at least onetransmitting resonance unit corresponding to the location of thewireless power receiver based on the measured current.

According to the embodiment, there is provided a power transmissionmethod of a wireless power transmitter for wirelessly transmitting powerto a wireless power receiver by using resonance. The power transmissionmethod includes applying detection power to a plurality of transmissionresonance units, measuring current generated from a transmission coilunit of the wireless power transmitter based on the detection power,determining at least one transmission resonance unit corresponding to alocation of the wireless power receiver based on the measured current,and transmitting the power through the at least one transmissionresonance unit that has been determined.

According to the embodiment of the disclosure, the wireless powertransmitter transmits energy through the transmission resonance unitcorresponding to the location of the wireless power receiver, therebyimproving the power transmission efficiency.

In addition, the wireless power transmitter concentrates the energytransmission through the specific transmission resonance unit, so thatthe energy can be inhibited from being wasted, and the magnetic fieldharmful to the human body can be reduced.

Meanwhile, other various effects may be directly or indirectly disclosedin the following description of the embodiment of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a wireless power transmission system accordingto one embodiment of the disclosure;

FIG. 2 is a circuit diagram showing an equivalent circuit of atransmission coil unit according to one embodiment of the disclosure;

FIG. 3 is a circuit diagram showing an equivalent circuit of a powersource and a transmitting unit according to one embodiment;

FIG. 4 is a circuit diagram showing an equivalent circuit of a receptionresonant coil, a reception coil unit, a smoothing circuit, and a loadaccording to one embodiment of the disclosure;

FIG. 5 is a view showing the structure of a wireless power transmitteraccording to one embodiment of the disclosure; and

FIG. 6 is a flowchart showing a method of transmitting power accordingto one embodiment of the disclosure.

DETAILED DESCRIPTION

In the following description, if detailed description about well-knownfunctions or configurations may make the subject matter of thedisclosure unclear, the detailed description will be omitted. Inaddition, terminologies to be described are defined based on functionsof components according to the embodiment, and may have meanings varyingaccording to the intentions of a user or an operator and customers.Accordingly, the terminologies should be defined based on the wholecontext throughout the present specification.

Hereinafter, the embodiment will be described with reference toaccompanying drawings.

FIG. 1 is a view showing a wireless power transmission system accordingto the embodiment.

Referring to FIG. 1, the wireless power transmission system includes apower source 10, a power transmission unit 20, a power reception unit30, a rectifying circuit 40 and a load 50.

The power generated from the power source 10 is provided to the powertransmission unit 20, such that the power transmission unit 20 transmitsthe power using resonance to the power reception unit 30, which isresonant with the power transmission unit 20 and has the same resonantfrequency value as that of the power transmission unit 20. The powertransferred to the power reception unit 30 is transferred via therectifying circuit 40 to the load 50. The load 50 may be a battery or apredetermined apparatus which needs power.

In detail, the power source 10 is an AC power source for supplying ACpower of a predetermined frequency.

The power transmission unit 20 includes a transmission coil unit 21 anda transmission resonant coil unit 22. The transmission coil unit 21 isconnected to the power source 10, such that an AC current flows throughthe transmission coil unit 21. When AC current flows through thetransmission coil unit 21, the AC current is induced to the transmissionresonant coil unit 22 physically spaced apart from the transmission coilunit 21 due to electromagnetic induction. The power transferred to thetransmission resonant coil unit 22 is transmitted using resonance to thepower reception unit 30 which forms a resonance circuit with the powertransmission unit 20.

According to the power transmission using resonance, the power can betransmitted between two LC circuits which are impedance-matched witheach other. The power transmission scheme using the resonance cantransmit the power farther than the power transmission scheme using theelectromagnetic induction with the higher power transmission efficiency.

The power reception unit 30 includes a reception resonant coil unit 31and a reception coil unit 32. The power transmitted from thetransmission resonant coil unit 22 is received in the reception resonantcoil unit 31, so that the AC current flows through the receptionresonant coil unit 31. The power transmitted to the reception resonantcoil unit 31 is transferred by electromagnetic induction to thereception coil unit 32. The power transferred to the reception coil 32is transferred through the rectifier circuit 40 to the load 50.

FIG. 2 is an equivalent circuit diagram of the transmission coil unit 21according to the embodiment. As shown in FIG. 2, the transmission coilunit 21 may include an inductor L1 and a capacitor C1, and form acircuit having a suitable inductance value and a suitable capacitancevalue.

The capacitor C1 may be a fixed capacitor or a variable capacitor. Whenthe capacitor C1 is the variable capacitor, the power transmission unit20 may control the variable capacitor for an impedance matching.Meanwhile, equivalent circuits of the transmission resonant coil unit22, the reception resonant coil unit 31, and the reception coil unit 32may be equal to that depicted in FIG. 2.

FIG. 3 is an equivalent circuit diagram of the power source 10 and thepower transmission unit 20 according to the embodiment. As shown in FIG.3, each of the transmission coil unit 21 and the transmission resonancecoil part 22 may include an inductor L1 or L2 and a capacitor C1 or C2having a predetermined inductance value and a predetermined capacitancevalue, respectively.

Especially, the capacitor C2 of the transmission resonant coil unit 22may be a variable capacitor, and the power transmission unit 20 mayadjust the variable capacitor to adjust a resonant frequency value forresonance.

FIG. 4 is an equivalent circuit diagram of the reception resonant coilunit 31, the reception coil unit 32, the rectifying circuit 40 and theload 50 according to the embodiment of the disclosure. As shown in FIG.4, each of the transmission resonant coil unit 31 and the reception coilpart 32 may include an inductor L3 or L4 and a capacitor C3 or C4 havinga predetermined inductance value and a predetermined capacitance value,respectively.

The rectifying unit 40 may include a diode D1 and a rectifying capacitorC5 such that the rectifying unit 40 converts AC power into DC power tobe output. Although the load 50 is denoted as a 1.3 V DC power source,the load 50 may be a battery or other devices requiring DC power.

Hereinafter, a wireless power transmitter 100 for transmitting energythrough a transmission resonance unit corresponding to the position of awireless power receiver and a method thereof will be described accordingto the embodiment of the disclosure.

FIG. 5 is view showing the structure of the wireless power transmitter100 according to one embodiment of the present invention.

Referring to FIG. 5, the wireless power transmitter 100 may include apower supply unit 11, a detection power applying unit 12, a currentmeasuring unit 13, a switch unit 14, a controller 15, a plurality oftransmission resonance units 20 and a pad 25. According to theembodiment, the transmission resonance units 20 may be arranged on thepad 25 in the 2D. According to one embodiment, the transmissionresonance units 20 may be arranged on the pad 25 in the 2D, so that thetransmission resonance units 20 may have the form of a matrix.

Meanwhile, as shown in FIG. 5, each transmission resonance unit 20 maycorrespond to the power transmission unit of FIG. 1, and remainingcomponents except for the transmission resonance unit 20 may be includedin the power source 10 of FIG. 1.

The transmission resonance units 20 correspond to a plurality ofresonance frequencies. The transmission resonance units may have thesame resonant frequency, or may have different resonant frequencies.

In addition, a portion of the transmission resonance units 20 may havethe first resonant frequency, and remaining transmission resonance units20 may have the second resonant frequency. In this case, the firstresonant frequency may differ from the second resonant frequency.

The pad 25 may have a rectangular shape, but the disclosure is notlimited thereto.

If a wireless power receiver 60 is located on the pad 25, the wirelesspower transmitter 100 may transmit energy to the wireless power receiver60 through a specific transmission resonance unit among the transmissionresonance units 20 placed on the pad 25. In this case, the wirelesspower receiver 60 may include the power reception unit 30, therectifying circuit 40, and the load 50, which are described withreference to FIG. 1, and may be installed in an electronic device suchas a portable terminal.

The power supply unit 11 generates AC power having a specific frequencyfor the energy transmission purpose, and the AC power may be transmittedto the transmission resonance units 20 through the switch unit 14.

The detection power applying unit 12 may generate detection power usedto detect the location of the wireless power receiver 60 and provide thedetection power to the switch unit 14. According to one embodiment, thedetection power may be a micro-power used to detect the wireless powerreceiver 60 provided on the pad 25. In this case, if the transmissionresonance units 20 have the same resonant frequency, the detection powermay be AC power having the same frequency as the resonant frequency.

The current measuring unit 13 measures the internal current generatedfrom the wireless power transmitter 100 by the applied detection power,and the measured current may be supplied to the controller 15. In thiscase, the controller 15 may detect the location of the wireless powerreceiver 60 based on the measured current.

Hereinafter, the principle in which the controller 15 detects thelocation of the wireless power receiver 60 based on the measured currentwill be described.

In the following description, it is assumed that a transmissionresonance coil unit 22 included in each transmission resonance unit 20has a self resonant frequency f1 due to inductor and capacitorcomponents connected to each other in parallel, and the transmissionresonance units 20 have the same self resonant frequency f1.

If the detection power having the resonant frequency f1 is applied toeach transmission resonance unit 20, the current measured in thewireless power transmitter 100 is minimized because the inductor and thecapacitor of each transmission resonance unit 20 appear in an open stateat the self resonant frequency f1, so that impedance is maximized.

If the wireless power receiver 60 approaches the transmission resonanceunits 20, the inductance component L1 of the transmission resonance unitand the inductance component L2 of the wireless power receiver arecoupled with each other, so that the mutual inductance component isdefined as following Equation 1.M=k√{square root over (L ₁ L ₂)},  Equation 1

In Equation 1, k represents a coupling coefficient, L1 represents selfinductance of the transmission resonance unit 20 corresponding to thelocation of the wireless power receiver 60, and L2 represents the selfinductance of the wireless power receiver 60.

The mutual inductance component M generated between the transmissionresonance unit 20 corresponding to the location of the wireless powerreceiver 60 and the wireless power receiver changes the self resonantfrequency f1 of the transmission resonance unit 60 and the wirelesspower receiver 60, and the changed self resonant frequency is called amutual-change resonant frequency f2.

In other words, if the wireless power receiver 60 is located on aspecific transmission resonance unit 20, the mutual-change resonantfrequency f2 may refer to the resonant frequency changed between mutualinductance components of the specific transmission resonance unit 20 andthe wireless power receiver 60.

The inductor and the capacitor of the transmission resonance unit 20corresponding to the location of the wireless power receiver 60 do nothave the maximum impedance value at the mutual-change resonant frequencyf2. Accordingly, if the detection power having the self resonantfrequency f1 is applied to the transmission resonance unit 20 close tothe wireless power receiver 60, the current measured in the wirelesspower transmitter 100 is increased.

In addition, as the wireless power receiver 60 more closely approachesthe specific transmission resonance unit 20, the mutual-change resonantfrequency f2 or the current measured in the wireless power transmitter100 is gradually increased. The controller 15 determines if the wirelesspower receiver 60 approaches the specific transmission resonance unit 20based on the variation in the mutual-change resonant frequency f2 or thecurrent.

The switch unit 14 performs a switching operation in order tosequentially supply the detection power, which is received from thedetection power applying unit 12, to the transmission resonance units20. In other words, the switch unit 14 sequentially supplies thedetection power to the transmission resonance units 20 according to thecontrol of the controller 15, so that the location of the wireless powerreceiver 60 can be detected.

In addition, the switch unit 14 may perform the switching operation insuch a manner that the power generated from the power supply unit 11 issupplied to the specific transmission resonance unit 20. In other words,the switch unit 14 performs the switching operation in such a mannerthat the power is supplied to the transmission resonance unit 20corresponding to the location of the wireless power receiver 60 and notsupplied to remaining transmission resonance units 20.

The transmission resonance units 20 may be arranged in the form of alattice or a matrix on the pad 25. In other words, the transmissionresonance units 20 may be arranged in such a manner that the area of thepad 25 is divided into a plurality of uniform areas.

In addition, the transmission resonance units 20 have the same shape andthe same size, but the present invention is not limited thereto.Meanwhile, although the total 12 transmission resonance units 20 areprovided in the form of a lattice according to the present embodiment,the disclosure is not limited thereto.

In addition, each transmission resonance unit 20 includes a transmissioncoil unit 21 and a transmission resonance coil unit 22.

The transmission coil unit 21 is connected to the switch unit 14, andhas AC current flowing therein to generate a magnetic field. Inaddition, the transmission coil unit 21 transmits the magnetic field tothe transmission resonance coil unit 22, which is physically spacedapart from the transmission coil unit 21, through the electromagneticinduction phenomenon.

If the transmission resonance coil unit 22 receives the magnetic fieldfrom the transmission coil unit 21, AC current is induced into thetransmission resonance coil unit 22. In addition, the transmissionresonance coil unit 22 supplies the energy stored therein to thewireless power receiver 60 through the resonance phenomenon. In thiscase, for the purpose of the wireless power transmission by theresonance, the self resonant frequency of the transmission resonancecoil unit 22 must be matched with the self resonant frequency of thereception resonance coil unit (not shown) provided in the wireless powerreceiver 60.

The transmission resonance coil unit 22 includes a capacitor 22 a, andthe capacitor 22 a may be a fixed capacitor having fixed capacitance ora variable capacitor having variable capacitance.

If the capacitor 22 a of the transmission resonance coil unit 22 is thevariable capacitor, the controller 15 may adjust the resonant frequencyby changing the capacitance of the capacitor 22 a of the transmissionresonance coil unit 22.

For example, on the assumption that the wireless power receiver 60 has afixed self resonant frequency, the wireless power transmitter 100 mayadjust the capacitance of the variable capacitor 22 a of thetransmission resonance coil unit 22 to have the resonant frequency equalto that of the wireless power receiver 60. In this case, the controller15 may previously store the information of the resonant frequency of thewireless power receiver 60.

Meanwhile, if the capacitor 22 a of the transmission resonance coil unit22 is a fixed capacitor, the capacitance of the capacitor 22 a may bepreset to the extent that the resonant frequency of the transmissionresonance coil unit 22 is equal to that of the wireless power receiver60.

The controller 15 may control the overall operation of the wirelesspower transmitter 100.

The controller 15 may perform a control operation to transmit power tothe wireless power receiver 60 through the specific transmissionresonance unit 20 corresponding to the location of the wireless powerreceiver 60 existing on the pad 25.

For example, as shown in FIG. 5, the transmission resonance units 20 maybe arranged in a 3×4 matrix with three rows and four columns, and thewireless power receiver 60 may be located on the transmission resonanceunits 20 provided in the second row and first column, the second row andsecond column, the third row and the first column, and the third row andthe second column.

In this case, the controller 15 controls the switch unit 14 to transmitpower to the wireless power receiver 60 only through the transmissionresonance units 20 provided at positions of the second row and firstcolumn, the second row and second column, the third row and the firstcolumn, and the third row and the second column.

In addition, the controller 15 may perform the control operation suchthat power is transmitted to the wireless power receiver 60 only throughthe transmission resonance unit 20, which is provided at a position ofthe second row and second column, most greatly overlapped with thewireless power receiver 60.

Through the above procedure, the wireless power transmitter 100 canconcentrate energy transmission on the wireless power receiver 60through the transmission resonance unit 20 corresponding to the locationof the transmission resonance unit 20. Accordingly, unnecessary powerconsumption may be inhibited.

Meanwhile, the controller 15 may previously store mutual-change resonantfrequency values according to the measured current in the form of alook-up table. Through the look-up table, the controller 15 can detectthe mutual-change resonant frequency f2 based on the detected currentfrom a current measuring unit 13, and may control the power supply unit11 so that the power supply unit 11 generates AC power having themutual-change resonant frequency f2.

In addition, the controller 15 sequentially controls the transmissionresonance units 20 while monitoring the information of the currentsupplied from the current measuring unit 13. In addition, the controller15 may detect the location of the wireless power receiver 60 on the pad25 based on the information of the current.

For example, the controller 15 applies the detection power having theself resonant frequency f1 to the transmission resonance unit 20provided at the position of the first row and first column through thecontrol of the switch unit 14. Then, if receiving the information of thecurrent from the current measuring unit 13, the controller 15 recognizesthe wireless power receiver 60 existing on the transmission resonanceunit 20 provided at the position of the first row and first column.

The controller 15 sequentially performs the above procedure with respectto each transmission resonance unit 20 to determine if the wirelesspower receiver 60 exists on a region of the pad 25 in which the relatedtransmission resonance unit 20 is located.

In addition, the controller 15 may previously set a threshold value inorder to determine a region, in which the wireless power receiver islocated, among regions corresponding to the transmission resonance units20. If the wireless power receiver 60 is located on a plurality ofregions, the variation in the quantity of current may be detected in allof the transmission resonance units 20 provided throughout the regions.

The controller 15 may determine the transmission coil unit located at aregion most greatly overlapped with the wireless power receiver bysetting the threshold value. Therefore, the controller 15 may determinethat the wireless power receiver 60 is located on the relatedtransmission resonance unit 20 only if the current received from thecurrent measuring unit 13 exceeds the preset threshold value.

If the location of the wireless power receiver 60 has been completelydetected, the controller 15 transmits energy through the transmissionresonance unit 20 corresponding to the location of the wireless powerreceiver 60. In other words, the controller 15 supplies AC powergenerated from the power supply unit 11 to the related transmissionresonance unit 20 through the control of the switch unit 14.

The wireless power transmitter 100 generates AC power having themutual-change resonant frequency f2 through the power supply unit 11 totransmit energy through the transmission resonance unit 20 correspondingto the location of the wireless power receiver 60. In other words, theactual energy transmission is achieved with the mutual-change resonantfrequency f2 instead of the self resonant frequency f1. In this case,the controller 15 may control the power supply unit 11 such that the ACpower having the mutual-change resonant frequency f2 is generated.

Meanwhile, although the wireless power transmitter 100 detects thelocation of the wireless power receiver 60 through the variation in thequantity of current according to the present embodiment, the disclosureis not limited thereto. In other words, the wireless power transmitter100 may detect the location of the wireless power receiver 60 by using apressure sensor located on the pad 25 instead of the detecting schemebased on the variation in the quantity of the current.

As described above, according to the embodiment of the disclosure, thewireless power transmitter 100 transmits energy through the specifictransmission resonance unit 20 corresponding to the location of thewireless power receiver 60 existing on the pad 25, thereby improvingenergy transmission efficiency to the wireless power receiver 60.

FIG. 6 is a flowchart showing a method of transmitting power by thewireless power transmitter 100 according to one embodiment of thedisclosure.

Hereinafter, the method of transmitting power by the wireless powertransmitter 100 according to one embodiment of the disclosure will bedescribed by making reference to the description of FIG. 5.

Referring to FIG. 6, the wireless power transmitter 100 sequentiallyapplies the detection power to a plurality of transmission resonanceunits 20 (step S101). According to one embodiment, the wireless powertransmitter 100 controls the switch unit 14 to sequentially apply thedetection power to the transmission resonance units 20. According to oneembodiment, the detection power may refer to the AC power having afrequency corresponding to the self resonant frequency f1 of thetransmission resonance unit 20.

Thereafter, the wireless power transmitter 100 measures internal currentbased on the detection power (step S103). According to one embodiment,the internal current of the wireless power transmitter 100 may becurrent output from the power supply unit 11, but the disclosure is notlimited thereto.

The measured current may be varied according to the impedancecharacteristic of the transmission resonance unit 20. In more detail, ifthe detection power having the frequency corresponding to the resonantfrequency f1 is applied to the transmission resonance unit 20, theimpedance of the wireless power transmitter 100 is most greatlyincreased, so that the measured current is minimized. If the detectionpower having the frequency different from the resonant frequency f1 isapplied to the transmission resonance unit 20, the impedance of thewireless power transmitter 100 is decreased, so that the measuredcurrent is increased.

Thereafter, the wireless power transmitter 100 determines if themeasured current exceeds the threshold value (step S105). According toone embodiment, the threshold value may refer to the minimum currentvalue required to detect the wireless power receiver located on thetransmission resonance units 20. In other words, if the measured currentis equal to or greater than the threshold value, the wireless powerreceiver 60 may be determined as being located on the specifictransmission resonance unit 20.

If the measured current value is equal to or greater than the thresholdvalue, the wireless power transmitter 100 determines that the wirelesspower receiver 60 is located on the specific transmission resonance unit20 (step S107). In other words, if the wireless power receiver 60 islocated on the specific transmission resonance unit 20, the resonantfrequency of the transmission resonance unit 20 corresponding to thelocation of the wireless power receiver 60 is changed into themutual-change resonant frequency f2, which has been described withreference to FIG. 5, due to the mutual inductance component. Inaddition, since the detection power having the frequency different fromthe resonant frequency f1 is applied to the transmission resonance unit20 corresponding to the location of the wireless power receiver 60, themeasured current may have a current value equal to or greater than thethreshold value.

Thereafter, the wireless power transmitter 100 determines thetransmission resonance unit 20 corresponding to the location of thedetected wireless power receiver 60 as the transmission resonance unitfor power transmission (step S109). According to one embodiment, thewireless power transmitter 100 may determine the transmission resonanceunit 20 corresponding to the location of the wireless power receiver 60among the transmission resonance units 20. For example, as shown in FIG.5, if the wireless power receiver 60 is located on the transmissionresonance units 20 provided at positions of the second row and firstcolumn, the second row and second column, the third row and firstcolumn, and the third row and second column, the wireless powertransmitter 100 may determine only the transmission resonance units 20,which are provided at positions of the second row and first column, thesecond row and second column, the third row and first column, and thethird row and second column, as the transmission resonance units 20 forthe power transmission to the wireless power receiver 60.

According to another embodiment, the wireless power transmitter 100 maydetermine only the transmission resonance unit 20 provided at theposition of the second row and second column most greatly overlappedwith the wireless power receiver 60 as the transmission resonance unit20 for the power transmission.

Thereafter, the wireless power transmitter 100 transmits power throughthe determined transmission resonance unit 20 (step S111). According toone embodiment, the wireless power transmitter 100 controls the switchunit 14 to transmit power to the wireless power receiver 60 through thedetermined transmission resonance unit 20.

As described above, according to the embodiment of the disclosure, thewireless power transmitter 100 transmits energy through the transmissionresonance unit 20 corresponding to the location of the wireless powerreceiver 60, thereby improving the power transmission efficiency.

In addition, the wireless power transmitter 100 concentrates the energytransmission through a specific transmission resonance unit 20, therebyreducing energy consumption, and reducing a magnetic field harmful tothe human body.

Although embodiments have been described with reference to a number ofillustrative embodiments thereof, it should be understood that numerousother modifications and embodiments can be devised by those skilled inthe art that will fall within the spirit and scope of the principles ofthis disclosure. More particularly, various variations and modificationsare possible in the component parts and/or arrangements of the subjectcombination arrangement within the scope of the disclosure, the drawingsand the appended claims. In addition to variations and modifications inthe component parts and/or arrangements, alternative uses will also beapparent to those skilled in the art.

What is claimed is:
 1. A wireless power transmitter for wirelesslytransmitting power to a wireless power receiver using resonance, thewireless power transmitter comprising: a power supply unit; a pluralityof transmission coils, each coil having a variable capacitor; adetection power applying unit that applies detection power using a firstfrequency to the transmission coils to detect a location of the wirelesspower receiver; a current measuring unit that measures variable currentvalue based on an impedance variance of the plurality of transmissioncoils based on the applied detection power; a controller that comparesthe measured current value of the applied detection power of each coilwith a threshold value, and that determines a location of the wirelesspower receiver when the measured current value exceeds the thresholdvalue; and a switch unit that sequentially applies the detection powerreceived from the detection power applying unit to the transmissioncoils, and operates such that a power generated from the power supplyunit is transmitted to one or a plurality of the transmission coilscorresponding to the location of the wireless power receiver detected bythe detection power according to the measured current value; wherein thepower supply unit supplies the power using a second frequency forcharging of the detected wireless power receiver; wherein the wirelesspower transmitter transmits the power having the second frequencythrough the one or a plurality of the transmission coils correspondingto the location of the wireless power receiver detected by the detectionpower; wherein the first frequency differs from the second frequency;wherein the second frequency is a power receive frequency of thedetected wireless power receiver and varies according to the wirelesspower receiver by the variable capacitor; wherein the threshold valuerefers to a minimum current value required to detect the wireless powerreceiver location; wherein the power supplied by the power supply unitis AC power, and wherein the second frequency differs from the firstfrequency by a mutual inductance component between a reception coil ofthe wireless power receiver and the one or plurality of the transmissioncoils corresponding to the location of the wireless power receiver. 2.The wireless power transmitter of claim 1, wherein the switch unit isoperated such that the power is transmitted only through a transmissioncoil that is most greatly overlapped with the wireless power receiver inthe transmission coils.
 3. The wireless power transmitter of claim 1,further comprising a pad provided thereon with the transmission coils,wherein the transmission coils are arranged in a form of a lattice or amatrix.
 4. A power transmission method of a wireless power transmitterfor wirelessly transmitting power to a wireless power receiver usingresonance, the power transmission method comprising: applying detectionpower to a plurality of transmission coils, each having a variablecapacitor using a first frequency by a switching of a switch unit;measuring variable current value based on an impedance variance of theplurality of transmission coils based on the applied detection power;comparing the measured current value of each of the transmission coils,with a threshold value; determining at least one transmission coilcorresponding to a location of the wireless power receiver when themeasured current value exceeds the threshold value; and transmittingpower to the at least one transmission coil corresponding to thelocation of the wireless power receiver detected by the detection powerusing a second frequency by a switching of the switch unit; wherein thefirst frequency differs from the second frequency, wherein the secondfrequency is a power receive frequency of the detected wireless powerreceiver and varies according to the wireless power receiver by thevariable capacitor, and wherein the second frequency differs from thefirst frequency by a mutual inductance component between a receptioncoil of the wireless power receiver and the at least one transmissioncoil corresponding to the location of the wireless power receiver. 5.The power transmission method of claim 4, wherein the power istransmitted to the at least one transmission coil according to themeasured current value.